Arc-Fault Circuit Interrupter (AFCI) Breaker

How it works

An arcing fault is an intermittent, high-frequency discharge across a gap — the kind produced by a cracked cord, a screw terminal that has worked loose, or insulation damaged by a staple. It can generate substantial heat without ever drawing enough current to trip a conventional breaker. An AFCI watches the waveform for the signature of arcing and trips on the pattern rather than the magnitude.

What the market looks like

Three brands dominate residential panels in North America — Square D, Siemens and Eaton — and breakers are specific to the panel they go into. Prices run CAD $50-$120 per breaker against CAD $10-$20 for a plain one, which is the honest reason older houses do not have them. Combination AFCI/GFCI devices exist and are increasingly the default in new construction. There is also an AFCI receptacle option for circuits where changing the breaker is impractical.

Features that actually matter

Combination-type detection

Detects both series arcing (a break in a conductor) and parallel arcing (between conductors). Combination type is the current standard and what codes require.

Panel compatibility

Not interchangeable between manufacturers, and sometimes not between panel generations within one manufacturer. Identify your panel precisely before buying.

Dual-function AFCI/GFCI

One device covering arc faults and ground faults. Usually the sensible choice where both are required.

Diagnostic trip indication

Better breakers signal why they tripped — arc fault, ground fault or overload — which turns a mystery into a starting point.

What it really costs

Up front

CAD $50-$120 per breaker.

Consumables

None.

What else you'll need

Electrician time, typically the larger cost on a retrofit. Doing several at once is far cheaper per circuit than one at a time.

Over five years

Nil.

Figures are typical street prices in Canadian and US dollars as of September 2026, gathered from public retail listings. They move with the season and with the exchange rate — treat them as a planning band, not a quote.

How it differs from the alternatives

Versus a standard breaker

A standard breaker protects the wire from overload and short circuit. It is blind to a glowing loose connection drawing ordinary current. Those are different problems and only one of them is covered without an AFCI.

Versus a GFCI

Different job entirely. GFCI protects people from shock by detecting current leaking to ground; AFCI protects the building from fire by detecting arcing. Many locations now need both.

The nuisance tripping question

AFCIs do trip on things a plain breaker ignores, and early generations had a poor reputation. Modern combination types are considerably better, and a repeated trip is more often a genuine fault — a damaged cord, a failing appliance, a loose backstab connection — than a false alarm. Investigate rather than replacing it with a plain breaker.

If your panel is obsolete

Some older panel types have known failure histories and no compatible AFCI. In that case the right purchase is a panel replacement assessment, not a breaker.

If not this, then what

• AFCI receptaclesProtects the circuit downstream of the outlet. Useful where the panel cannot take a breaker.
• An electrical inspectionIf the house is old and has never been assessed, the inspection should come before the shopping.